Assessment of Annual Tracheobronchial Effective Dose from Indoor Radon Inhalation in Selected Residential Buildings in Southwestern Nigeria

Background and Purpose: Radon-222 is a major human health challenge among all sources of ionizing radiation. For most people, the greatest exposure to radon comes from homes and affects mainly the respiratory tract, especially the tracheobronchial region. This work assesses the annual tracheobronchial effective dose from indoor radon inhalation in residential buildings with different covering materials for walls, ceilings and floor using different dosimetric lung models.Method: A total of 180 residential buildings with commonest combination of covering materials in some cities in South-western Nigeria were investigated using an active electronic radon gas detector, RAD 7. The commonest combination of covering materials were (A): paint, paint, carpet; (B): paint fiber board, plastic tiles; (C): paint, fiber board, ceramic tiles for walls, ceilings and floors respectively.Result: The mean indoor radon concentration measured ranged between 23.08 Bq m-3 and 72.14 Bq m-3 for all the residential buildings investigated. Buildings with covering materials C, presented the highest radon concentration. Generally, the mean indoor radon concentration for all combinations of covering materials in all the cities investigated were found to be lower than the recommended action level of 200 Bqm-3 and the reference level of 100 Bqm-3 set by International Commission on for Radiation Protection and World Health Organization respectively. The annual tracheobronchial effective dose estimated for the different lung dose models ranged from 0.91 mSv – 3.27 mSv for combination (A), 1.00 mSv - 3.60 mSv for combination (B) and 1.09 mSv – 3.94 mSv for combination (C). It revealed that the more recent model gives greater value of the annual tracheobronchial effective dose. It was observed that only the annual tracheobronchial effective doses obtained by the James model presented values that are within the recommended ICRP intervention level of (3-10) mSvy-1. Other models gave values of annual tracheobronchial effective doses below the ICRP recommended intervention levels.Conclusion: These imply that all the residential buildings and the different combination of covering materials surveyed in this work will not pose any radiological hazard to the inhabitants.Key words: Indoor Radon Inhalation, Radon-222, annual tracheobronchial effective dose, residential buildings